Process for the producing of pentenenitriles

ABSTRACT

The present invention relates to a process for the preparation of pentenenitriles. In this process the 3- or 4-pentenenitriles are produced by reacting 2-methylglutarimide, ethylsuccinimide, and/or their precursors, such as 4-cyanovalerimide, 2-methyl-4-cyanobutyrimide, 4-cyanovaleric acid, 2-methyl-4-cyanobutyric acid, 3-cyanovalerimide, 2-ethyl-3-cyanopropionimide, 3-cyanovaleic acid, and 2-ethyl-3-cyanopropionic acid, in the vapor phase at temperatures of 200° to 600° C. in the presence of an acidic solid catalyst, such as acidic molecular sieves, acidic clays, bridged or pillared clays, bulk oxides, and acidic phosphates.

The present invention relates to a process for the preparation ofpentenenitriles. Pentenenitriles, more particularly 3-pentenenitrile and4-pentenenitrile, can result in adiponitrile by reaction with hydrogencyanide.

The invention more specifically consists of a process for thepreparation of pentenenitriles by the use, in the vapour phase, of2-methylglutarimide and/or of ethylsuccinimide and/or of theirprecursors, in the presence of an acidic solid catalyst chosen inparticular from acidic molecular sieves, acidic clays, bridged clays (orpillared clays), bulk oxides and acidic phosphates.

During the preparation of adiponitrile by hydrocyanation of butadiene,with the intermediate production of pentenenitriles, large amounts ofmethylglutaronitrile and ethylsuccinonitrile are inevitably obtained.These by-products currently have only very few industrial outlets andmust largely be incinerated.

It is therefore entirely desirable to enhance the value of suchby-products and this is one of the aims of the present invention. Thisis because the compounds employed in the present process,2-methyl-glutarimide and/or ethylsuccinimide, as well as theirprecursors, can be prepared from methylglutaronitrile or fromethylsuccinonitrile.

2-Methylglutarimide can be employed directly or in the form of one ofits precursors, such as in particular 4-cyanovaleramide,2-methyl-4-cyano-butyramide, 4-cyanovaleric acid or2-methyl-4-cyanovaleric acid.

Likewise, ethylsuccinimide can be employed directly or in the form ofone of its precursors, such as in particular 3-cyanovaleramide,2-ethyl-3-cyanopropionamide, 3-cyanovaleric acid or2-ethyl-3-cyanopropionic acid.

2-Methylglutarimide and its precursors are the most important and thepreferred substrates among those which can be employed in the presentprocess, in particular because of the higher proportion ofmethylglutaronitrile available and because of the better results whichthey provide.

2-Methylglutarimide can be prepared, for example, by reaction ofmethylglutaronitrile with dodecanoic acid, as described in an article inthe Journal of Organic Chemistry, 36, pages 3050 et seq. (1971). It canalso be prepared by reaction of methylglutaric acid with ammonia, asdescribed in another article in the Journal of Organic Chemistry, 22,pages 1728 et seq. (1957).

The acidic molecular sieves employed are in particular acidic zeolitesof pentasil structure, such as, for example, ZSM-5, ZSM-11, ZSM-12,ZSM-22, ZSM-23, ZSM-48, mordenite or ferrierite, and acidic zeolites offaujasite structure, such as, for example, zeolite X or zeolite Y.

The zeolites of pentasil structure are more particularly zeolites ofZSM-5, ZSM-12, ZSM-11, ZSM-22, ZSM-23, ZSM-48, mordenite and ferrieritetype having the general formula (I) expressed in terms of ratios ofoxides:

    M.sub.2/n O•X.sub.2 O.sub.3 •mSiO.sub.2 •pH.sub.2 O (I)

in which:

M represents a component chosen from hydrogen, NH₄ and mono-, di-, tri-and tetravalent metals, M being at least in part a hydrogen atom,

X represents a trivalent element chosen from Al, Ga, Fe and B,

n represents a number from 1 to 4,

m represents a number equal to or greater than 2,

p represents a number from 0 to 40.

The zeolites of faujasite structure are more particularly those havingthe general formula (II) expressed in terms of ratios of oxides:

    M.sub.2/n O•Z.sub.2 O.sub.3 •dSiO.sub.2 •xH.sub.2 O (II)

in which:

M represents a component chosen from hydrogen, NH4 and mono-, di-, tri-and tetravalent metals, M being at least in part a hydrogen atom,

Z represents a trivalent element chosen from Al, Ga, Fe and B,

n represents a number from 1 to 4,

d represents a number equal to or greater than 2,

x represents a number from 5 to 100.

The zeolites used in the context of the invention are preferably thosein the formula (I) or (II) of which the oxide used in combination withsilica is that of a trivalent metal, in particular Al or Ga.

Preference is generally given to the acidic zeolites in the formula (I)or (II) of which M is chosen from hydrogen, NH₄, alkali metals, such as,for example, Na, K, Li, Rb or Cs, alkaline-earth metals, such as, forexample, Be, Mg, Ca, Sr or Ba, rare-earth metals, such as, for example,La or Ce, or transition metals, such as, for example, Fe.

For a more detailed description of acidic clays, reference may be madeto Patent FR-A-2,622,575, which is incorporated in the present text byreference.

Preference is given, in the process of the invention, to the use ofsmectites, such as, for example, montmorillonites, beidellites,nontronites, hectorites, stevensites and saponites.

Bridged clays, which can be used as catalysts in the present process,are clays between the sheets of which have been introduced bridges orpillars which maintain a basal spacing. The basal spacing is the sum ofthe thickness of a sheet of the clay and of the interfoliar spacing.

The preparation of these bridged clays has been described in particularin Patent FR-A-2,563,446 and in Patent FR-A-2,618,143.

Preference will generally be given, as starting clay, to beidellites.

Bridging of the clays can be achieved in particular using aluminium,vanadium, molybdenum, zirconium, iron, niobium, tantalum, chromium,lanthanum, cerium, titanium and gallium hydroxides or mixed hydroxidesof a number of these metals.

These bridged clays can be modified, in particular by the action of adihalogen, of an ammonium halide or of an acid, such as sulphuric acidor hydrohalic acids. The halogen thus optionally introduced ispreferably chlorine or fluorine.

Use is preferably made, in the process of the invention, of clays,particularly beidellites, bridged using aluminium hydroxide.

The bulk oxides are metal oxides, mixtures of metal oxides or modifiedmetal oxides, in particular modified by the action of a dihalogen, of anammonium halide or of an acid, such as sulphuric acid or hydrohalicacids. The halogen thus optionally introduced is preferably chlorine orfluorine.

Mention may be made, as non-limiting examples, of SiO₂ /Al₂ O₃, SiO₂/Ga₂ O₃, SiO₂ /Fe₂ O₃ and SiO₂ /B₂ O.sub.₃ mixtures, halogenatedaluminas, such as in particular chlorinated aluminas and fluorinatedaluminas, sulphated zirconia, niobium oxide or tungsten oxide.

The acidic phosphates which can be used in the process of the inventionare in particular, by way of examples, boron phosphates, alone or as amixture with alumina or with silica, corresponding to various H₃ BO₃ /H₃PO₄ molar ratios introduced during the synthesis, lanthanum phosphate,aluminium phosphates corresponding to various Al₂ O₃ /H₃ PO₄ molarratios introduced during the synthesis, phosphorus pentoxide/silicamixtures (generally known as UOP catalysts), aluminophosphates ofzeolite structure (AlPO) and silicoaluminophosphates of zeolitestructure (SAPO).

The process is implemented continuously.

The catalyst used can be arranged in a stationary bed or be employed ina fluidized bed. It can be used as a mixture with inert solids, in orderto increase the contact surface area.

The process is generally implemented at a temperature of 200° C. to 600°C. and preferably of 250° C. to 500° C.

The contact time, defined as the ratio methyl isobutyl ketone, orethers, such as dibutyl ether or dimethoxyethane. Water can also be usedas solvent when precursors of 2-methylglutarimide or of ethylsuccinimideare employed.

They can also be introduced in conjunction with an inert carrier gas;this joint introduction can be carried out in the form of a mixture orin the form of separate simultaneous introductions.

The inert carrier gas can consist of a gas or a mixture of gases whichare inert under the reaction conditions, such as, for example, nitrogenor argon.

The substrate employed, in particular 2-methylglutarimide and/or itsprecursors, represents from 5% to 100% by weight with respect to thetotal weight of gases introduced into the reaction and preferably from10% to 100%.

The process of the invention generally results in the formation of amixture of pentenenitriles, 2-pentenenitrile, 3-pentenenitrile and4-pentenenitrile. These last two pentenenitriles can be converted intoadiponitrile by reaction with hydrogen cyanide.

The following examples illustrate the invention.

The following procedure will be used, except when otherwise mentioned,in the examples.

The following are successively charged, onto the sintered glass, in areactor arranged vertically (tube made of Pyrex glass with a length=15cm and with a diameter=2 cm): quartz grains (from 0.63 to 1.25 mm) overa height of 1.2 cm, the catalyst of ZSM-5 type (0.25 cm³, 0.5 cm³, 1 cm³or 2 cm³, depending on the examples) having a particle size of 0.25-1.25mm, and then a second layer of quartz with a height of 1.2 cm.

The catalyst is then calcined overnight at 475° C.

The reaction is carried out under a 0.3 liter/hour nitrogen stream at atemperature of 450° C., except when otherwise mentioned.

The dissolved substrate is then injected via a syringe driver.

The injection flow rates will be specified for each example: they areexpressed in grams of solution per hour.

After running for approximately 1 hour, the test proper lasts 1 hour,during which the products exiting from the reactor are trapped in aseries of three receivers, the first at room temperature and thefollowing ones cooled by ice.

Analysis of the reaction products and of the unconverted substrate iscarried out by gas chromatography (GC).

The following are calculated for each test: between the volume of thecatalyst and the total gas flow rate (2-methylglutarimide and/orethylsuccinimide and/or their precursors+solvent, if appropriate+carriergas, if appropriate) at the chosen temperature, generally varies from0.1 second to 50 seconds and most often from 0.2 second to 10 seconds.

The pressure is not critical. It is generally between a pressure lowerthan atmospheric pressure and 10 MPa (100 bar) and preferably between0.01 MPa (0.1 bar absolute) and 5 MPa (50 bar).

The 2-methylglutarimide and/or the ethylsuccinimide and/or theirprecursors can be introduced into the reactor containing the catalysteither in the molten state or in solution in a solvent which issubstantially inert under the reaction conditions.

Use may be made, as solvents, of any compound which is vaporized underthe reaction conditions, which does not induce harmful side reactionsand in which the substrate or substrates employed are soluble. In thepresent text, a substrate is regarded as soluble in a compound when itcan be dissolved in the proportion of at least 5 grams per liter of thesaid compound at 50° C.

Mention may be made, as non-limiting examples of solvents, of nitrites,such as acetonitrile, propionitrile, valeronitrile, adiponitrile ormethylglutaronitrile, ketones, such as acetone or

the degree of conversion (DC) of the substrate: % of the substrateconverted with respect to that which has been charged;

the yields (YY) of pentenenitriles and of methylglutaronitrile formed:molar % of these compounds formed with respect to the substrate charged;

isomeric distribution of the pentenenitriles formed.

EXAMPLES 1 TO 11

These tests were carried out by using 2-methylglutarimide as substrate.

Tests of various acidic zeolites of ZSM-5 type of general formula (I) inwhich X represents Al and exhibiting various SiO₂ /Al₂ O₃ molar ratios(value of m in the formula (I)):

Zeolite 1

SiO₂ /Al₂ O₃ =51

100% of the components M in the formula (I) are H

n=1

Zeolite 2

SiO₂ /Al₂ O₃ =350

100% of the components M in the formula (I) are H

n=1

The operating conditions are those given in the general proceduredescribed above.

The concentration of 2-methylglutarimide in the injected solution is 15%by weight/weight and the injection flow rate of this solution is 3.5g/h.

The contact time (ct) is indicated (in seconds) for each of theexamples.

The results obtained are combined in Table 1 below.

The abbreviations MGI, PN, PN2, PN3, PN4 and MGN used have the followingmeanings:

MGI=2-methylglutarimide

PN=pentenenitriles

PN2=2-pentenenitrile

PN3=3-pentenenitrile

PN4=4-pentenenitrile

MGN=methylglutaronitrile.

EXAMPLES 12 AND 13

These tests were carried out by using 2-methylglutarimide as substrate.

The operating conditions are those given in the general proceduredescribed above but the tests are carried out at different temperatures.

The concentration of 2-methylglutarimide in the injected solution is 15%by weight/weight and the injection flow rate of this solution is 3.5g/h.

The catalyst used is zeolite 1 (1 cm³).

The contact time (ct) is indicated for each of the examples.

The results obtained are collated in Table 2 below.

                  TABLE 1                                                         ______________________________________                                                                      YY % PN                                                                       PN2/PN3/                                                                      PN4                                                    Catalyst         DC %  distri- YY %  ct                                Examples                                                                             (volume) Solvent MGI   bution  MGN   (in s)                            ______________________________________                                        Example 1                                                                            Zeolite 2                                                                              Aceto-  98    75      0     1.6                                      (2 cm.sup.3)                                                                           nitrile       40/44/16                                        Example 2                                                                            Zeolite 2                                                                              Aceto-  96    77      6     0.8                                      (1 cm.sup.3)                                                                           nitrile       28/53/19                                        Example 3                                                                            Zeolite 2                                                                              Aceto-  80    65      4     0.4                                      (0.5 cm.sup.3)                                                                         nitrile       16/61/23                                        Example 4                                                                            Zeolite 2                                                                              aceto-  62    47      1     0.2                                      (0.25 cm.sup.3)                                                                        nitrile       10/63/27                                        Example 5                                                                            Zeolite 1                                                                              Aceto-  79    60      6     0.2                                      (0.25 cm.sup.3)                                                                        nitrile       15/61/24                                        Example 6                                                                            Zeolite 1                                                                              Aceto-  89    63      9     0.4                                      (0.5 cm.sup.3)                                                                         nitrile       28/52/20                                        Example 7                                                                            Zeolite 1                                                                              Aceto-  99    67      12    0.8                                      (1 cm.sup.3)                                                                           nitrile       41/44/15                                        Example 8                                                                            Zeolite 2                                                                              Acetone 36    26      1     0.5                                      (0.5 cm.sup.3)          4/60/36                                        Example 9                                                                            Zeolite 2                                                                              Acetone 68    52      0     1.8                                      (2 cm.sup.3)           11/62/27                                        Example                                                                              Zeolite 2                                                                              Acetone 28    17      0     0.2                               10     (0.25 cm.sup.3)         4/59/37                                        Example                                                                              Zeolite 2                                                                              Acetone 50    39      1     0.9                               11     (1 cm.sup.3)            7/61/32                                        ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                                     YY % PN                                                                       PN2/PN3/PN4                                             Temp.           DC %  distri-  YY %  ct                                Examples                                                                             (in °C.)                                                                       Solvent MGI   bution   MGN   (in s)                            ______________________________________                                        Example                                                                              400     Aceto-  68    41       14    0.8                               12             nitrile       15/64/21                                         Example                                                                              350     Aceto-  22     9        9    0.8                               13             nitrile        6/71/23                                         ______________________________________                                    

EXAMPLES 14 TO 17

These tests were carried out by using various substrates which areprecursors of 2-methylglutarimide:

Example 14, carried out with 4-cyanovaleramide

Example 15, carried out with 2-methyl-4-cyanobutyramide

Example 16, carried out with 4-cyanovaleric acid

Example 17, carried out with 2-methyl-4-cyanobutyric acid.

The operating conditions are those given in the general proceduredescribed above.

The concentration of substrate in the injected solution is 50% byweight/weight and the injection flow rate of this solution is 1 g/h.

The contact time (ct) is indicated for each of the examples.

The results obtained are collated in Table 3 below.

                  TABLE 3                                                         ______________________________________                                                                      YY % PN                                                                       PN2/PN3/                                                                DC %  PN4                                                    Catalyst         sub-  distri- YY %  ct                                Examples                                                                             (volume) Solvent strate                                                                              bution  MGN   (in s)                            ______________________________________                                        Example                                                                              Zeolite 1                                                                              Water    82   17      18    2.7                               14     (2 cm.sup.3)           51/37/12                                        Example                                                                              Zeolite 1                                                                              Water    81   17      19    2.7                               15     (2 cm.sup.3)           52/35/13                                        Example                                                                              Zeolite 1                                                                              Aceto-  100   17       6    4.5                               16     (2 cm.sup.3)                                                                           nitrile       65/24/11                                        Example                                                                              Zeolite 2                                                                              Aceto-  100   40      11    4.5                               17     (2 cm.sup.3)                                                                           nitrile       51/37/12                                        ______________________________________                                    

EXAMPLES 18 AND 19

These tests were carried out by using 2-methylglutarimide as substrate.

The operating conditions are those given in the general proceduredescribed above but the tests are carried out with differentconcentrations of 2-methylglutarimide in the injected solution.

The injection flow rate of these solutions is 3.5 g/h.

The catalyst used is zeolite 2 (0.5 cm³).

The contact time (ct) is indicated for each of the examples.

The results obtained are collated in Table 4 below.

                  TABLE 4                                                         ______________________________________                                                                      YY % PN                                                                       PN2/PN3/                                                                      PN4                                                    MGI              DC %  distri-                                                                              YY %   ct                                Examples                                                                             (% w/w)  Solvent MGI   bution MGN    (in s)                            ______________________________________                                        Example                                                                              20       Aceto-  66    55     3      0.4                               18              nitrile       9/64/27                                         Example                                                                              30       Aceto-  54    43     2      0.4                               19              nitrile       7/64/29                                         ______________________________________                                    

EXAMPLES 20 TO 25

These tests were carried out by using 2-methylglutarimide as substrateand by employing different acidic catalysts.

These catalysts are commercially available products.

Only boron phosphate was prepared in the laboratory, according to thefollowing procedure:

417.4 g of H₃ PO₄ (2.9 mol) are introduced into a 1 l reactor equippedwith a central stirrer and a reflux condenser;

then 180 g (2.9 mol) of boric acid H₃ BO₃, sieved at 300 μm, areintroduced with stirring;

the mixture is heated at reflux for one hour and is then cooled to roomtemperature;

the mixture is calcined for 3 h at 500° C.

The operating conditions are those given in the general proceduredescribed above, with a catalyst volume of 1 cm³, a concentration of2-methylglutarimide in the injected solution of 33% by weight/weight, anitrogen flow rate of 1 liter/hour and an injection flow rate of 1.5g/h, acetonitrile being used as solvent.

The contents of the traps are analysed after the first hour ofoperation.

The results obtained are collated in Table 5 below: degree of conversion(DC) of the substrate and the yield (YY) of pentenenitriles formed.

                  TABLE 5                                                         ______________________________________                                                                     DC %    YY %                                     Examples Catalyst            MGI     PN                                       ______________________________________                                        Example 20                                                                             BPO.sub.4   B/P = 0.85  60    27                                     Example 21                                                                             Mordenite   SiO.sub.2 /Al.sub.2 O.sub.3  =                                                            59    25                                              ZM760       25                                                       Example 22                                                                             Zeolite β                                                                            SiO.sub.2 /Al.sub.2 O.sub.3  =                                                            80    23                                                          6                                                        Example 23                                                                             Faujasite HY                                                                              SiO.sub.2 /Al.sub.2 O.sub.3  =                                                            61    10                                              ZF520       10                                                       Example 24                                                                             Mordenite   SiO.sub.2 /Al.sub.2 O.sub.3  =                                                            44     9                                              ZM510       5                                                        Example 25                                                                             HCl-treated All of Ca.sup.2+                                                                          47     7                                              montmorillonite                                                                           exchanged                                                ______________________________________                                    

We claim:
 1. A process for the preparation of pentenenitriles, saidprocess comprising reacting at least one of 2-methylglutarimide,ethylsuccinimide, and precursors thereof selected from the groupconsisting of 4-cyanovaleramide, 2-methyl-4-cyanobutyramide,4-cyanovaleric acid, 2-methyl-4-cyanobutyric acid, 3-cyanovaleramide,2-ethyl-3-cyanopropionamide, 3-cyanovaleric acid, and2-ethyl-3-cyanopropionic acid, in the vapor phase, at a temperature of200° C. to 600° C., in the presence of an acidic solid catalyst selectedfrom the group consisting of acidic molecular sieves, acidic clays,bridged clays (or pillared clays), bulk oxides, and acidic phosphates.2. The process according to claim 1, wherein 2-methylglutarimide isemployed directly or in the form of one of its precursors selected fromthe group consisting of 4-cyanovaleramide, 2-methyl-4-cyanobutyramide,4-cyanovaleric acid, and 2-methyl-4-cyanobutyric acid.
 3. The processaccording to claim 1, wherein the acidic molecular sieves employed arezeolites of pentasil structure.
 4. The process according to claim 3,wherein the zeolites of pentasil structure are ZSM-5, ZSM-11, ZSM-12,ZSM-22, ZSM-23, ZSM-48, mordenite and ferrierite type having the formula(I) expressed in terms of ratios of oxides:

    M.sub.2/n O•X.sub.2 O.sub.3 •mSiO.sub.2 ·pH.sub.2 O (I)

in which: M represents a component chosen from hydrogen, NH₄ and mono-,di-, tri- and tetravalent metals, M being at least in part a hydrogenatom; X represents a trivalent element chosen from Al, Ga, Fe and B; nrepresents a number from 1 to 4; m represents a number equal to orgreater than 2; and p represents a number from 0 to
 40. 5. The processaccording to claim 1 wherein the bulk oxides used are metal oxides,mixtures of metal oxides or metal oxides modified by the action of adihalogen, of an ammonium halide, or of an acid.
 6. The processaccording to claim 5, wherein the bulk oxides used are selected fromSiO₂ /Al₂ O₃, SiO₂ /Ga₂ O₃, SiO₂ /Fe₂ O₃ and SiO₂ /B₂ O₃ mixtures,halogenated aluminas, sulphated zirconia, niobium oxide, and tungstenoxide.
 7. The process according to claim 1, wherein the acidicphosphates used are selected from the group consisting of boronphosphates, alone or as a mixture with alumina or with silica,corresponding to various H₃ BO₃ /H₃ PO₄ molar ratios introduced duringthe synthesis, lanthanum phosphate, aluminum phosphates corresponding tovarious Al₂ O₃ /H₃ PO₄ molar ratios introduced during the synthesis,phosphorus pentoxide/silica mixtures, aluminophosphates of zeolitestructure (AlPO), and silicoaluminophosphates of zeolite structure(SAPO).
 8. The process according to claim 1, which is carried out at atemperature of 250° C. to 500° C.
 9. The process according to claim 1,wherein said at least one of 2-methylglutarimide, ethylsuccinimide, andprecursors thereof is introduced into a reactor containing the catalysteither in the molten state or in solution in a solvent which issubstantially inert under reaction conditions.
 10. The process accordingto claim 9, wherein said at least one of 2-methylglutarimide,ethylsuccinimide, and precursors thereof is introduced into the reactorin solution in a solvent selected from nitrites, ketones, and ethers.11. The process according to claim 9, wherein a precursor of2-methylglutarimide or ethylsuccinimide is employed in solution inwater.
 12. The process according to claim 5, wherein the acid issulphuric acid or hydrohalic acids.
 13. The process according to claim5, wherein the halogen is chlorine or fluorine.
 14. The processaccording to claim 6, wherein the halogenated aluminas are chlorinatedaluminas or fluorinated aluminas.
 15. The process according to claim 9,wherein said nitrites are selected from acetonitrile, propionitrile,valeronitrile, adiponitrile, and methylglutaronitrile.
 16. The processaccording to claim 9, wherein said ketones are selected from acetone andmethyl isobutyl ketone.
 17. The process according to claim 9, whereinsaid ethers are selected from dibutyl ether and dimethoxyethane.